“Here I am.”: An expression of modesty and eagerness. He went with alacrity to fulfill his father’s command although he knew that his brothers hated him. [From Mechilta Beshallach , second treatise, introduction]

from…Hebron: But is not Hebron on a mountain? It is stated: “And they ascended in the south, and he came as far as Hebron” (Num. 13:22). But [it is to be understood that he sent him] from the deep counsel of the righteous man who is buried in Hebron (i.e., Abraham), to fulfill what was said to Abraham between the parts (Gen. 15:13). [From Gen. Rabbah 84:13]

and he came to Shechem: a place destined for misfortune. There the tribes sinned, there Dinah was violated, there the kingdom of the house of David was divided, as it is said: “And Rehoboam went to Shechem” (I Kings 12:1). [From Sanh. 102a]

They have traveled away from here: They removed themselves from brotherhood.

נסעו מזה: הסיעו עצמן מן האחוה:

‘Let us go to Dothan.’: Heb. נֵלְכָה דֹתָינָה, to seek regarding you legal pretexts (נִכְלֵי דָתוֹת), by which they could put you to death. According to its simple meaning, however, it is a place-name, and a Biblical verse never loses its simple sense.

and we will see what will become of his dreams: Rabbi Isaac said, This verse says: “Expound on me.” [I.e., this verse demands a midrashic interpretation.] The Holy Spirit says thus: They (the brothers) say, “Let us kill him,” but the verse concludes: “and we will see what will become of his dreams.” Let us see whose word will stand up, yours or Mine. It is impossible that they (the brothers) are saying,“and we will see what will become of his dreams,” because, since they will kill him, his dreams will come to nought. [From Tan. Buber, Vayeshev 13]

“Let us not deal him a deadly blow.”: Heb. לֹא נַכֶּנוּ נָפֶשׁ. Literally, let us not smite him the soul. [This is equivalent to] מַכַּת נֶפֶשׁ, [let us not deal him] a deadly blow, which means death. [From Targum Onkelos]

לא נכנו נפש: מכת נפש זו היא מיתה:

22And Reuben said to them, "Do not shed blood! Cast him into this pit, which is in the desert, but do not lay a hand upon him," in order to save him from their hand[s], to return him to his father.

to save him: The Holy Spirit testifies for Reuben that he said this only to save him, so that he would [be able to] come and take him out of there. He said, “I am the firstborn and the eldest of them all. The sin will be attributed only to me.” [from Gen. Rabbah 84:15]